bazel: upgrade rules_python to 2.3.2 and enforce explicit init py

[openroad-ci]

Summary

Upgrades @rules_python from 1.8.5 to 2.3.2, removes the previous quiet = True warning suppression, and configures explicit __init__.py generation for Bazel 9 hermeticity.

Motivation & Background

1. Fix Upstream Unhashed Pip Warnings & Remove quiet = True:

   • Transitive pip dependencies (such as those from @grpc) previously triggered repetitive warnings (WARNING: requirement file has been generated without hashes...) during bzlmod evaluation. This was previously silenced via quiet = True in PR bazel: silence pip warnings #11143 (f166b4132a).
   • Upstream lockfile hash pinning (initiated in grpc/grpc#42415 and merged in grpc/grpc#42637) combined with rules_python 2.x completely eliminates these unhashed warnings at the source.
   • We can now safely drop quiet = True from pip.parse.

2. Explicit __init__.py Creation:

   • Rules Python 2.x deprecates implicit __init__.py creation.
   • Configured rules_python_config.explicit_init_py(default = True) in MODULE.bazel and --incompatible_default_to_explicit_init_py in .bazelrc, ensuring zero deprecation noise across both local and transitive external targets (such as sv-lang).

3. Security & Hermeticity:

   • Enforces SHA-256 hash pinning on all downloaded wheels.
   • Eliminates host python interpreter fallback paths during execution.

4. Remote Caching:

   • Preserves deterministic action graph inputs and wheel artifacts for remote caching.

5. Downstream Test Parity:

   • Updated test/downstream/MODULE.bazel to match the rules_python version bump.

Verification

Validated locally using ./etc/bazel-hermetic:

• //bazel:requirements.test (PASSED)
• //docs:sphinx_build_test (PASSED)
• //bazel:tclint (PASSED)
• //bazel:yamlfix (PASSED)
• //:openroad_py (PASSED)
• //test:openroad_public_test (PASSED)
• //test:openroad_py_public_test (PASSED)
• //test:openroad_lib_restricted_test (PASSED)
• //test:rules_verilator_dev_dep_test (PASSED)
• //docs/src/scripts:test_extract_utils (PASSED)

[gemini-code-assist]

Code Review

This pull request upgrades rules_python to version 2.3.2 and configures explicit __init__.py behavior using the --incompatible_default_to_explicit_init_py flag and the rules_python config extension. The reviewer suggested also configuring the rules_python config extension in the downstream test workspace to maintain parity and prevent potential build failures.

[sombraSoft]

FYI @oharboe
I have enabled the warnings again just so not to hide warnings if anything upstream breaks in the future.

[sombraSoft]

Another small win for our build's hermeticity 🚀